Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$166.83	7.709%	$179.6909	$179.69	$179.70	$179.70
Purchase #2	$58.97	11.103%	$65.5174	$65.52	$65.50	$65.50
Purchase #3	$60.72	4.211%	$63.2769	$63.28	$63.30	$63.30
Purchase #4	$219.96	12.519%	$247.4968	$247.50	$247.50	$247.50
Purchase #5	$53.31	10.453%	$58.8825	$58.88	$58.90	$58.90
Purchase #6	$199.45	12.600%	$224.5807	$224.58	$224.60	$224.60
Purchase #7	$172.55	5.152%	$181.4398	$181.44	$181.45	$181.40
7 purchase totals =	$931.79		$1,020.8850	$1,020.89	$1,020.95	$1,020.90